Microsoft has admitted that, despite being one of the dominant names in IT for over 30 years, it had little or no experience or expertise around software standards until the company was mid-way through the process of getting OOXML approved by the ISO.

Compared to Windows you could argue that it is. But really it’s kind of a meaningless statement: no system which is connected to a network or used by human beings is completely secure, and if it was it would probably be useless.